Knife



H. w. TrrTLE KNIFE v Filed Dec. l2, 1929 Patented Dec. l, 1931 UNITEDSTATES PATENT OFFICE HARRY W. TITTLE, F AKRON, OHIO, ASSIGNOR TO THE B.F. GOODRICE COMPANY. 0F NEW YORK, N. Y., A CORPORATION OF NEW YORK KNIFEApplication led December 12, 1929. Serial No. 413,509.

This invention relates to knives and more cspcciall y to hand operated,electrically heated cutting tools which may be usefully employed in therubber industry for cutting rub ber sheets.

The chief object of the invention is to provide au improved electricallyheated knife of convenient size, Weight, and shape for manual handling.Other objects will be manifest.

Of the accompanying drawings:

Fig. l is a perspective view of my improved knife, in its preferredform, in atypical operative association with the work.

Fig. 2 is a longitudinal section through the knife.

Fig. 3 is a section on line 3 3 of Fig. 2.

Fig. 4 is a section of line 4 4 of Fig. 2.

Referring to Fig. 2 of the drawings, the knife comprises a handle ofWood or other' dielectric and heat resisting material and a blade 11 ofloop form and of suitable electric resistance metal such as nichromesteel adapted to be heated by electric current supplied thercto by apair of electrodes 12, 13. The latter are composed of electricallyconductive metal, of low electrical resistance, in the form ofcylindrical rods which are mounted in respective longitudinal bores inthe handle 10. The electrodes l2, 13 project beyond one end of thehandle and support the blade 11 which is attached at one of its ends toboth electrodes in any suitable manner, preferably b slotting theelectrodes and welding the lade in the slots, as isiclearly shown inFig. 3. The other ends of the electrodes 12, 13 are disposed within thehandle 10 and to them are secured respective electrical conductors 14,15 of a flexible cable 16 having connection with a suitable source ofelectric current (not shown).

The blade 11 preferably has a rounded point at its end remote from thehandle 10 and preferably has both lateral edges sharpened adjacent itspointed end. The blade is formed with a longitudinal slot 17 which eX-tends from its attached end between the electrodes 12, 13 to a pointadjacent its opposite end. Thus the blade is formed as a generallyU-shaped structure or loop having a sharpened outer edge and having apoint at the outer end of the loop. The knife is wider and thicker atits rear end than at its forward, sharper end, with the result that thelatter has greater resistance to electrical current and consequentlyattains the greatest heat. y

A typical example of the use for which my improved knife is especiallyadapted is illust-rated in Fig. 1 of the drawings, in which 18 is asheet of unvulcanized rubber and 19 is a template of metal laid thereon,the rubber being severed by drawing the pointed end of the knifethereover while guiding it by contact with the edge of the template.Used in the manner described, the knife requires to be heated only to adull redness to melt the rubber, and such heating of the blade may beeffected with electric current of relatively low voltage, say 2 or 3volts, at 40 amperes.

The pointed end of the blade permits the accurate cutting of intricatedesigns from the rubber sheet 18, and the sharp lateral edges of theblade may be utilized for cutting simpler designs or for cutting thickersheets of rubber. Because the blade is not heated to incandescense, itisnot subject to oxidation with resultant rapid dulling of its cuttingedge. Consequently frequent sharpenin is avoided, and wetting of theblade, to lu ricate the same, is not required.

By heating the blade directly as a result of its own resistance, insteadof by conduction from a heating element, I provide a tool of lighterWeight and having greater convenience of handling. The blade may beheated with substantial uniformity throughout its structure, and itspoint, which is the portion subject to greatest use, may be keptuniformly hot.

The invention is susceptible of modification within the scope of theappended claims.

I claim:

1. In a cutting tool the combination of a handle, a blade supportedthereby and comprising a generally U-shaped structure of high resistancemetal having a sharpened edge terminating at a cutting point, andelectrical conductors connected with the respective legs of the U-shapedstructure, the electrical resistance of the blade being greater near thepoint. f

2. In a knife the combination of a handle, a cuttin blade supportedthereby and formed of a re atively hard alloy capable of maintaining acutting edge with a longitudinal slot open at one end of the blade, andelecJ trical conductors attached to said blade at opposite sides of saidslot, said blade being provided with a plurality of sharp edgesterminating in a pomt.

In Witness whereof I have hereunto set my hand this 6th day of December,1929.

HARRY W. T ITTLE.

